Some embodiments of the present disclosure may relate to a multi-output power supply apparatus and an output circuit thereof.
A power supply apparatus may provide a plurality of output voltages depending on an electronic product where it is employed.
A general multi-output power supply apparatus converts input power into a plurality of alternating current (AC) voltages through a transformer and rectifies the plurality of AC voltages to output a plurality of direct current (DC) voltages.
However, in the general multi-output power supply apparatus, when a voltage level of one of the plurality of DC voltages is varied by the transformer, the voltage having the varied voltage level has an influence on other DC voltages.
An example of a multi-output power supply apparatus including an image voltage and a backlight unit voltage will hereinafter be described. The multi-output power supply apparatus may perform a controlling operation based on a feedback from the secondary side image voltage of the transformer. When a load of the image voltage is decreased, a resonant frequency may be increased, such that a voltage swing width of a primary side resonant capacitor is narrowed. Therefore, the input voltage of the transformer may drop.
In addition, since the number of secondary side windings is determined depending on an input voltage of the backlight unit, when a high input voltage is required in the backlight unit, leakage inductance may be increased.
Therefore, when the load of the image voltage is decreased in a circuit having a large amount of leakage inductance as described above, power from the transformer may be decreased due to the input voltage drop, such that a large voltage drop may occur in the backlight unit voltage, that is, cross-regulation may be increased.
In addition, such a voltage drop due to the cross-regulation may have an influence on a dimming pulse, such that it may be difficult to accurately control dimming.
Patent Document 1 relates to a power supply apparatus for a plasma display panel (PDP), and Patent Document 2 relates to a multi-output switching power apparatus.